Gaseous electric discharge device



May 14, 1935 w. DE GROOT ETAL 2,001,528

GASEOUS ELECTRIC DISCHARGE DEVICE Filed Sept. 14, 1952 Inventors:

Their Attorney.

Patented May 14, 1935 UNITED STATES PATENT OFFICE GASEOUS ELECTRIC DISCHARGE DEVICE Application September 14, 1932, Serial No. 633,144 In the Netherlands September 18, 1931 5 Claims.

The present invention relates to gaseous electric discharge devices generally and more particularly the invention relates to such devices in which the gaseous atmosphere consists wholly or 5 in part of a condensible metal vapor.

Various means have been proposed heretofore to reduce the rate of condensation of the metal vapor in the container of the device during the operation of said device and in certain instances the container has been surrounded by an envelope and the space between said envelope and. said container has been evacuated or filled with a gas having poor heat conducting characteristics to reduce the heat radiation from the walls of said container which reduces the rate of condensation of the metal vapor in said container to give greater stability to the operating characteristics of the device.

The object of the present invention is to reduce to a minimum the rate of condensation of a metal vapor in the container of a gaseous electric discharge device having an envelope surrounding said container. Another object of the invention is to provide internal means for directing in a desired direction the radiations emanating from the gaseous electric discharge in a gaseous electric discharge device. Still further objects and advantages attaching to the device and to its use and operation will be apparent to those skilled 30 in the art from the following particular description and from the appended claims.

The invention attains the first of its objects by providing a thin metal film on the inner walls of the envelope surrounding the container of the gaseous electric discharge device. Said film reflects a large percentage of the invisible heat radiations emanating from the gaseous electric discharge in the device while at the same time it is transparent to a large percentage of the visible light radiations. The reflected heat radiations are directed back to the gaseous electric discharge device to raise the temperature thereof which reduces to a minimum the rate of condensation of the metal vapor in the container of the device and the energy given up by the heat radiations when said radiations hit the reflecting surface also serves the same purpose. The invention attains the second of its objects by providing a metal film covering part of the inner wall of the envelope surrounding the container ofthe electric discharge device and said film is adapted to reflect the visible radiations in a desired direction. The invisible, heat radiations, such as the infra-red rays, which are also reflect- 55 ed by the film, give up a large percentage of their energy to the container and to the film which reduces the rate of condensation of the metal vapor in said container.

In the drawing accompanying and forming part of this specification two embodiments of the invention are shown, in which Fig. 1 is a front elevational schematic view of one embodiment of the invention, and

Fig. 2 is a similar view of another embodiment of the invention.

Like numbers denote like parts in both figures.

Referring to Fig. 1 of the drawing the new and novel gaseous electric discharge device comprises a spherical container I having electrodes 2 and 3 sealed therein. Said electrode 3 is the anode and is supported by wire 4. Said wire 4 is covered by insulating material, where desired. Said electrode 2 is the cathode and consists of a coiled wire filament coated with a material having high electron emissive characteristics and is known in the art as a Wehnelt cathode. Said container I has a filling consisting of a condensible metal vapor, such as mercury, sodium, cadmium, etc., and a gas, such as argon.

Container I is surrounded by a spherical glass envelope 5 and said container I is supported in said envelope 5 by current inleads I sealed into the stem 6 of said envelope 5. That part of the inner wall of said envelope 5 surrounding said stem 6 is covered with a metal film 8, indicated by dotted lines, which acts as a mirror. Said film 8 is applied to the inner wall of said envelope 5 by chemical or electrolytic deposition and consists of chromium, or silver, for example. The

space between said container I and said envelope 5 is filled with air, or with a gas being a poor conductor of heat such as argon. Where desired said space is evacuated.

Both visible and invisible radiations are generated by the gaseous electric discharge which takes place between said electrodes 2 and 3 during the operation of the device. The rays emitted in the direction of said film 8 are reflected thereby and the visible radiations are directed ina desired direction while the invisible radiations, that is the infra-red, or heat radiations, give up most of their energy to the container I and to film 8 to maintain said container 1 at a high temperature which reduces to a minimum the rate of condensation of the condensible metal vapor therein to increase the operating efficiency and stability of the device.

The embodiment of the invention shown in Fig. 2 is similar to that shown in Fig. 1 with the exception that in this embodiment the metal film 2, 8, which covers the entlre'surtace o! the inner wall of said envelope 5, is approximately 1p. in thickness and transmits the visible radiations but reflects the invisible or heat radiations back to said container I where their energy is given up to maintain the temperature of said container I and the pressure of the vapor therein at a high level which increases the operating efliciency. and the stability of the gaseous electric discharge device.

Where, the above described devices have a gaseous filling consisting wholly or in part of sodium vapor a thin film of copper is used on the inner wall of said envelope 5. In many instances it is desirable to protect the reflecting surface of the copper film during the manufacture of the device to avoid oxidizing said surface and this is done by app ying a thin film of gold over said surface. Said films are applied to said envelope 5 by placing a filament of said material in said envelope 5. The envelope 5 is then evacuated and the copper filament is heated first to deposit copper particles on the inner wall of said envelope 5, the gold filament is then heated to deposit gold particles over said copper particles. The gold film prevents the oxidation of the refleeting surface of the copper film when container I is inserted in envelope 5 during the manufacture of the device. It will be understood, of course, that those parts of the inner wall of envelope 5 of the device illustrated in Fig. l which it is desired to keep free of metal film 8 must be covered during the above described process. Where cadmium vapor is used a film of silver is desirable.

While we have shown and described and have pointed out in the annexed claims certain novel features of the invention, it will be understood that various omissions, substitutions and changes in the forms and details of the device illustrated and in its use and operation may be made by those skilled in the art without departing from the broad spirit and scope of the invention, for example, the metal film is applied to the outer wall of the container l with the same eflect as that described above, but the preferred embodiments of our invention are those shown and described above and further container I and envelope 5 are concentric cylinders where desired.

What we claim as new and desire to secure by Letters Patent of the United States is:--

1. An electric discharge device comprising a container, electrodes sealed therein, a gaseous atmosphere therein comprising a condensible metal vapor, and an envelope surrounding said container, a film of metal interposed between the inner wall of said envelope and-the outer wall of said container and adapted to reflect the infra-red radiations back to said container to prevent condensation of said metal vapor.

2. An electric discharge device comprising a container, electrodes sealed therein, a gaseous atmosphere therein comprising a condensible metal vapor, and an envelope surrounding said container, a film of metal on the inner wall of said envelope adapted to reflect the infra-red radiations back to said container to prevent condensation of said metal vapor.

3. An electric discharge device comprising a container, electrodes sealed therein, a gaseous atmospherc therein comprising a condensible metal vapor, and an envelope surrounding said container, a film of metal on the inner wall of said envelope adapted to transmit the visible light radiations and to reflect the infra-red radiations back to said container to prevent condensation of said metal vapor.

4. An electric discharge lamp device comprising a container, electrodes sealed therein, a vaporizable material therein, a heat conservator for said container, an infra-red ray reflecting material interposed between said container and said heat conservator to maintain an efiective vapor pressure in said container during the operation of said lamp.

5. An electric discharge lamp device comprising a container, electrodes sealed therein, a vaporizable material therein, a heat conservator for said container, a reflecting coating interposed between said heat conservator and said container to reflect the infra-red rays back to said con-- tainer to maintain an effective vapor pressure in said container during the operation of said device emitted by said lamp.

WILLEM DE GROOT. MARI JOHAN DRUYVESTEYN. 

